The invention is directed to a surface testing device comprising a base frame, a vibratory system including a sensor carrier and spring elements for reciprocating the sensor carrier and coupled thereto, and an exciter for operating the system in vicinity of its resonance frequency.
Known surface testing devices of this type (U.S. Pat. No. 4,682,498) serve, among other things, to test the surfaces of flat steel slabs, heavy plates or other test pieces for defects or other characteristics by means of sensors which are reciprocated preferably close above the surfaces to be tested. Either an individual torsion spring bar or a pair of torsion spring bars which are excited in the same direction serve as spring elements.
The vibratory systems constructed from such torsion spring bars bring about numerous undesirable problems. For example, the costly work which is required in exchanging defective parts such as the torsion spring bars, their bearings, the sensor carriers or the like, the visual check of the torsion spring bars or their bearings for the purpose of early detection of damages, which visual check is desirable but only possible at high expense, e.g. the disassembly of the system parts, the impossibility of adjusting the zero position of the sensor carrier or the sensors during operation, the high manufacturing costs and outlay caused by the absence of standard structural component parts, particularly torsion spring bars, and the fact that the adjustment of the resonance and natural frequency of the vibratory system to a preselected or prescribed value is only possible by means of re-equipment, the resonance and natural frequency being determined by the vibrating masses and the dimensioning of the torsion spring bars. But, above all, the required large constructional volume, which is a function chiefly of the required minimum dimensioning of the torsion spring bars, is troublesome and in particular results in considerable space related problems in the testing of surfaces of slabs, or the like, from a plurality of sides, since it presents an obstacle to the combination of a plurality of vibratory systems in a single compact surface testing station.